The invention relates to a breathing-controlled inhalation device for dry powder, particularly dry powder which has been mixed with medicines.
For a long time, one of the primary methods for the treatment of respiratory diseases has been the introduction of suitable agents into the respiratory tract. In this regard, the devices used for thisxe2x80x94often also as mechanisms to stimulate transportxe2x80x94have gained an ever-growing significance because of the increase in the number of respiratory diseases in the last number of years. In particular, breathing-controlled devices, which offer a mild alternative to propellant-controlled devices, are being increasingly used, since they do not have the unpleasant effect of stimulating colds.
A device of this type is known from DE 40 04 904 A1, in which the agent is kept ready on the periphery of a dosing drum and is regulated radially. The inside of the dosing drum contains a control unit for the active output of the divided inhalation amount from open dosing recesses in a radially outwards direction. Moreover, the bottom of the equally-angled distributed arranged dosing recesses forming slides are centrally cam-controlled. Since this control mechanism is additionally activated by a control key which lies practically along the whole length of the device, the expenditure in this regard is considerable. Moreover, the dosed medicines can be added by means of a forced emptying of the dosing recess. This can lead to a dangerous over-dosage. In terms of volume, the space which remains for the reservoir represents only a fraction of the pocket-format device.
DE 198 25 434 A1 describes an inhalation device in which the dosing device is made taut before the intake of the medicine and is held in this condition on a stopper which can be moved during inhalation. The dosing device is released and accelerated during inhalation, so that the accelerated movement is abruptly interrupted in that the stopper on the dosing device strikes the casing or the bottom of the casing. This sudden interruption of the rotation of the dosing device results in the powdery medicine being released from the dosing cavity at greater speed and being widely distributed in the air channel. This design is also relatively complicated and, in addition, demonstrates the lack of inclusion of flow-orientated air guidance. The air channel has a straight design and does not permit any circulation or turbulence of the agents to be inhaled.
DE 43 40 768 A1 describes a device for the inhalation of powdery agents, which is provided with a special turbulence chamber in spiral form, the complicated construction design of which case disadvantageous. Although, the turbulence chamber does facilitate a certain evenness in the distribution of the powder, the spiral turning of the turbulence chamber leads increasingly to friction and resistance points which prevent complete passage of the particles.
Furthermore, in U.S. Pat. No. 5,699,789, an inhaler for dry powder, in which a dosing conveyor is provided, has a reservoir container projecting into the air-flow channel which takes a predetermined amount of dry powder and is positioned inside the air guiding unit. The air which passes through the air-flow channel has to move around both the reservoir container and a nose located near the inlet opening. In this way, a certain turbulence of the air is achieved, though it cannot be ensured that all the conducted dry powder is conveyed through the inlet opening in a homogenously distributed manner.
In EP-A-938907 an inhalation device for dry powder is described in which inwardly projecting plates are provided alternately in the air-flow channel in order to achieve a turbulence of the air. Because of the high volume of clearance areas in this device it cannot be ensured that the total amount of dosed powder is conveyed outwards during inhalation.
A similar inhalation device is shown in the WO-A-993305. Powder residue can also remain in the device in this case, which adulterates the dosage.
The invention therefore relates to the creation of a breathing-controlled inhalation device of the type mentioned at the beginning, which, as a result of a simple design with few simple components, can be cost-effectively manufactured, has a small size, is provided with a double dose protector, and with which a complete and even distribution of the dry powder during the inhalation procedure can be attained. Furthermore, a method is provided which enables a complete and even respirable distribution in the breath of the dry powder to be inhaled.
The invention overcomes the disadvantageous of prior art devices with an air guiding unit consisting of an essentially cylindrical central component which is provided alternately with semi-spherical indentations reaching from opposite walls of the central component into the air-flow channel, the air-flow channel having a rising inhalation area in the application area of the inhalation device, and with a dosing conveyor positioned directly downwards in front of the inhalation area. An air guiding unit designed in this manner permits a very effective and complete distribution of the dry powder during the inhalation procedure, since the air which has been drawn in circulates and the rising particles can be mixed with each other in an optimal way.
By means of this special arrangement of the inhalation area, the dry powder can, when required, get directly into the air-flow channel and can from there be directly drawn in. In this way, the risk of the intrusion of moisture or of an unintentional proportional loss of portioning during inhalation is reduced.
In a preferred embodiment of the invention the casing is provided with an air inlet which is positioned downwards opposite the inhalation area. The opening of the device in the form of the air inlet permits an increased intake of the particles, independent of the remaining air.
Moreover, the inhalation device of the invention comprises a dosing conveyor in the form of a flat slide number having a laterally oriented dosing bole hole for receiving a predetermined amount of dry powder from the reservoir. The slide member is movable between a first position in which it receives the dry powder and a dosing position in which the borel hole is directly in front of the inhalation area of the air guiding unit. In the dosing position, the slide keeps the reservoir essentially locked.
In this way double dose protection can be ensured, since only the amount of dry powder located in the dosing drill hole is available for each inhalation procedure. Should the inhalation procedure be broken off or interrupted, the remainder of the dry powder located in the dosing drill hole is conveyed back into the reservoir or is removed from the inhalation area and is thereby not available for a further inhalation procedure.
A favourable design feature here ensures that the slide is held in a spring-loaded start position in which the reservoir is locked and that the slide is moveable against a spring resistance into the dosing position. A spring-controlled movement mechanism guarantees that accidental escape, unintended intrusion of moisture or an unintentional actuation of the device are practically excluded. Moreover, an important advantage of this design is that, because of the simplicity of the functional construction, besides the necessary readjusting spring, only one moving part (dosing conveyor) is required, which further guarantees the constant availability for use of the device and minimizes the risk of any possible errors.
The air guiding unit can have a single-part or multi-part design, whereby glass or plastic as cost-effective materials have proved themselves to be particularly suitable. Other suitable materials, such as metals, may also of course be used for the, manufacture of the air guiding unit.
Furthermore, the advantages of the invention are achieved in that the acceleration of the air-flow is effected by means of cross section narrowings in the air guiding unit in the form of semi-spherical indentations which project alternately into the airflow channel in the air guiding unit from opposite walls of the central component. The air circulation and flow guiding provided in this special method make possible effective turbulence of the individual dry powder particles. The movements of the air spread the particles evenly and guarantee optimum distribution at the moment of inhalation.
By means of the concentration of the flow of particles with kinetic energy their movement and distribution capacity is increased and a possible loss of energy caused by gravity is compensated, which makes for an overall improvement of the turbulence effect.